ABSTRACT
During the last decade internal combustion engines have become deemed to be one of the main cause of pollution. As a consequence, governments and policy makers are strongly pushing towards electric technologies and in particular battery electric vehicles (BEVs), despite the huge efforts of scientists and researchers in designing cleaner and more efficient hybrid powertrains employing both electric motors and thermal machines. Hybrid electric vehicles (HEVs) have demonstrated capability of delivering low emissions while reducing costs compared to the BEVs. This work is focussed on the study of a series hybrid vehicle (also commonly called a Range Extended Electric Vehicle – REEV) equipped with a range extender running on hydrogen fuel. The study has been conducted mainly at a numerical level by simulating the performance of the commercial BMW i3 over the common NEDC and WLTP drive cycles and then comparing the results with the original powertrain in terms of energy, fuel consumption and emissions. All the modelling activities and optimisations have been carried out using the commercial software GT-Suite by Gamma Technologies.
The vehicle model has been validated against the experimental data provided in literature and other previous works from the authors, while the internal combustion engine model setup relies on experimental data coming from a previous project carried out at Argonne National Laboratory. Interestingly, the present study also takes into account the different fuel storage system employed for the hydrogen, characterized by a high ratio between its total weight and the weight of fuel contained. In that respect an evaluation of the differences in weight and tank volume, performance and energy consumption of both the original and the hydrogen vehicles have been carried out.
Finally, the simulations demonstrate that the increased weight due to the different fuel storage system does not heavily affect the performance and the energy consumption of the entire vehicle. In addition the improved results in terms of fuel consumption establish that hydrogen internal combustion engines, with their higher efficiency (higher than 44%), are a viable solution for range extender applications while giving the opportunity of a thorough optimisation on the choice of the battery size in order to maximise range and minimise weight and cost while maintaining the desired driveability.
